Suspensory graft fixation with adjustable loop length

ABSTRACT

A suspensory fixation device has an elongated anchor member adapted to be transversely situated at the exit of a bone tunnel. A graft supporting loop member formed of a pair of parallel suture limbs extending from a bight portion is suspended transversely from the anchor member and has a loop length which is adjustable so the graft ligament can be supported in the bone tunnel at varying distances from the anchor member. When a graft ligament is attached to the saddle end of the loop member, the length may be shortened by pulling distally on the pair of limbs to pull the graft ligament into the bone tunnel. When tension is applied to the loop member by the graft pulling the loop proximally, the bight portion of the suture automatically locks the graft supporting loop member in place.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. Non-Provisional patentapplication Ser. No. 15/620,920 filed on Jun. 13, 2017, which is adivision of and claims the benefit of priority from U.S. Non-Provisionalpatent application Ser. No. 14/574,946 filed Dec. 18, 2014, which claimsthe benefit of priority from U.S. Provisional Patent Application Ser.No. 61/964,907, entitled “Suspensory Graft Fixation with Adjustable LoopLength”, and filed on Jan. 16, 2014. The content of the above-identifiedapplication is incorporated herein by reference in its entirety

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to surgical devices for the repair andreconstruction of soft tissue injuries. In particular, this inventionrelates to devices and methods for the surgical implantation ofreplacement (autograft or allograft or artificial) ligament grafts.Still more particularly, the invention relates to the surgical repair ofanterior cruciate ligament grafts.

Description of the Prior Art

The repair and reconstruction of torn or damaged soft tissues is acommon surgical procedure. For example, replacement graft ligaments maybe secured at the site of the original ligament. The procedure generallyinvolves drilling bone tunnels into adjacent bones at the site of theoriginal ligament and securing a graft ligament within these bonetunnels. In many applications, such as in the knee joint, suchprocedures may be performed arthroscopically. The graft ligament may bean autograft, an allograft, a xenograft, or it may be totally artificialand synthetic. Common types of anterior cruciate ligament (ACL) grafts,for example, include ones which may be autologous or allograftbone-patellar tendon-bone or soft tissue (such as semitendinosus andgracilis tendons), both types harvested by techniques well known tothose skilled in the art.

The graft ligaments may be secured within the bone tunnels in a varietyof ways. Of prime importance is the degree to which they can withstandpullout forces prior to complete healing. For example, it is known touse interference screws inserted parallel to the tunnel axis to compressthe ends of the graft ligament against the wall of the bone tunnel tosecure the graft ligament and promote tissue in-growth.

Suspensory graft fixation devices have been developed to secure a graftligament in a bone tunnel. One such device is described in U.S. Pat. No.8,852,250 (Lombardo et al.), entitled Graft Fixation Implant, assignedto the assignee hereof and incorporated by reference herein. Suspensorygraft fixation devices work by lying transversely across the opening ofa bone tunnel and generally take the form of an elongated anchor memberwhich suspends a graft retaining loop from a fixation point on thesurface of a bone to which the graft is to be attached (in this case, afemur). The elongated member has an axis and a pair of suture receivingapertures symmetrically situated on the axis on opposite sides of thecenter of the elongated member. In ACL procedures the elongated member,often called a button, is adapted to be situated transversely across theexit opening of the bone tunnel on the lateral femoral cortex so that asupporting loop, generally made of suture material, can be suspendedfrom the button and can extend into the bone tunnel from the suturereceiving apertures of the button. The suture loop supports one end of agraft ligament passed through the loop. The term “suture” as used hereinmay be any type of filamentous material such as a biocompatible orbioabsorbable filament, ribbon, tape, woven or non-woven materialcapable of providing the loop support and the frictional resistancerequired by the device described herein. In an arthroscopic proceduressuch as an ACL reconstruction the elongated anchor member is initiallyaligned with the axis of the bone tunnel, and pulled through the tunnelto the exit at the distal end on the lateral femur. For such suspensorygraft fixation devices to be able to support a graft ligament and to beproperly transversely situated at the exit of the bone tunnel, thesuture loop and the bone tunnel must both be long enough to enable theelongated member to “flip” from an axially aligned orientation to atransverse orientation when it exits the bone tunnel.

Since the supporting loop of such a suspensory device is most often of afixed length, graft fixation requires preparation of a graft ligament ofpredetermined length. Furthermore, because prior art suspensory graftfixation devices have fixed loop lengths they are produced in multiplesizes (ranging, for example, from loop lengths of 15 mm to 60 mm in 5 mmincrements in the case of XO Button® implants made by ConMedCorporation, Largo, Fla.) in order to accommodate various graft andtunnel lengths that may be encountered during a surgical procedure. Thefixed graft length and variations in tunnel and loop lengths make priorart suspensory ligament fixation challenging.

Recently, suspensory devices have been made with adjustable looplengths. See, for example, U.S. patent application 2010/0256677,(Albertorio et al.) published Oct. 7, 2010 and entitled IntegratedAdjustable Button-Suture-Graft Construct with Two Fixation Devices. Ithas been found that the adjustability of the loop length of a suspensorygraft fixation device may be achieved in a manner considerably lesscomplex than that described in the aforementioned publication.

At times surgeons may encounter situations where they cannot produce abone tunnel of adequate length to receive a ligament graft suitable forsuspensory fixation. A predetermined length of graft ligament isrequired to engage a predetermined portion of the bone tunnel for properhealing. For example, a so-called short tunnel ACL reconstruction maypresent a relatively small (narrow) femur which does not enableformation of an adequately long bone tunnel which means, in turn, thesuspensory anchor member cannot be advanced far enough out of the tunnelto flip yet keep enough contact between the graft and the bone tunnelwall. Use of an adjustable loop in such situations could neverthelessenable the surgeon to proceed with a suspensory-type repair. Accordinglyit is an object of this invention to produce a suspensory graft ligamentrepair system suitable for short tunnel repairs.

In instances in which soft tissue is to be pulled into a bone tunnel,such as ACL reconstruction, it is desired to have an adjustable loop tosimplify the procedure and maximize the bone to soft tissue interface.

It is an object of this invention to produce a suspensory graft fixationdevice adapted to lock the size and position of the graft supportingloop after it has been set at a desired length.

It is also an object of this invention to automatically lock the graftsupporting loop by pulling it in one direction relative to the anchormember, and to vary the length of the graft supporting loop, to resizeit, by pulling it in the opposite direction.

SUMMARY OF THE INVENTION

These and other objects of this invention are achieved by a suspensorygraft fixation device for securing a replacement ligament graft in abone tunnel comprising an elongated anchor member adapted to be situatedtransversely adjacent the exit of the bone tunnel, a graft supportingelement in the form of a loop adapted to support the replacementligament graft a predetermined variable distance away from the exit, andmeans for adjusting the distance between the exit of the bone tunnel andthe graft, and means for locking the graft supporting element tomaintain the distance at a set point.

Another aspect of the invention is the method of suspensory fixation ofa graft ligament comprising the steps of providing a suspensory graftfixation device as described above, providing a filamentous material tobe used as a graft supporting element in the form of a loop, arrangingthe filamentous material in such a way as to enable it to be placed in alocking position, pulling the ends of the filamentous material in orderto shorten the length of the supporting loop and locking the loop lengthat a desired point.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the anchor portion of a suspensory graftfixation device constructed in accordance with the principles of thisinvention.

FIG. 2 is a view of the anchor portion of the suspensory graft fixationdevice of FIG. 1 showing its engagement with a filamentous material suchas suture.

FIG. 3 is a close-up view of the suspensory graft fixation device ofFIG. 2 showing the winding path of suture.

FIG. 4 is a cross-sectional view of the suspensory graft fixation deviceof FIG. 3 showing the winding path of suture.

FIG. 5 is a perspective view of an alternate embodiment of a suspensorygraft fixation device threaded with a filamentous material.

FIG. 6 is a perspective view of an alternate embodiment of a suspensorygraft fixation device using a single hollow core suture threaded withinthe apertures of an anchor member, and a separate bight member.

DESCRIPTION OF THE INVENTION

A suspensory graft fixation device 10 constructed in accordance with theprinciples of this invention is shown in the drawings. Device 10comprises an elongated anchor member 12 and suture in the form offilamentous strand 40. Anchor member 12 has a first end 14, a second end16, an axis 18, and a pair of suture receiving apertures 20 and 22.Anchor member 12 has a top surface 24 and a bottom surface 26 (best seenin FIG. 4). Bottom surface 26 is sometimes referred to as the proximalsurface and is intended to be placed adjacent a bone tunnel exit. Asused herein, the term “proximal” refers to the side of the bonecontaining the bone tunnel (i.e., extending inwardly away from thesurface of the lateral femur in an ACL procedure), and the term “distal”refers to the side of the bone against which the transverse anchormember rests (i.e., extending outwardly away from the surface on thelateral femur). Apertures 20 and 22 are situated on opposite sides of acentral bridge portion 28 extending between them. In the preferredembodiment apertures 20 and 22 are formed in a pocket/recess 30 set intop surface 24. The recess 30 has a perimeter 32 at the intersection ofrecess 30 with top surface 24, the purpose of which will be explainedlater. Anchor member 12 also has a suture return aperture 34 extendingbetween top and bottom surfaces 24 and 26 as well as a pulling aperture36. While one could provide one return aperture for each suture limb, inthe preferred embodiment both limbs pass through one return aperture.

Device 10 is designed to have anchor member 12 operate with afilamentous strand 40 suitable for following a tortuous path through thevarious apertures of anchor member 12. In the preferred embodimentfilamentous strand 40 is a single length of appropriately sized suture.The term “suture” as used herein may be used interchangeably with“filamentous material” and, as described above, will be understood tomean any biocompatible or bioabsorbable strand of material which can,when combined with anchor member 12, operate to support a replacementgraft in the manner described below. The suture may comprise a pluralityof parallel strands although in the preferred embodiment a single strandfolded on itself has been found sufficient depending on size. As will beunderstood below, the combination of filamentous strand 40 with thefeatures of anchor member 12 can perform different functions atdifferent points along the path 29 of the suture through the aperturesof anchor member 12.

To aid in describing the winding path 29 of the filamentous material,which in the preferred embodiment is a hollow-core suture, we will startat apertures 20 and 22, and describe the various sections of path 29through which the suture is threaded. To facilitate the explanation ofwinding path 29 we will define suture strand 40 as folded on itself toform a central bight portion 42, thus creating two limbs 44 and 46extending from bight 42. Each limb has a length extending from the bightto the free, unattached end of the limb. Referring to FIG. 3, suture leg44 is passed down through receiving aperture 20 into section 50, acrossthe bottom of graft supporting loop 70 into section 52, up on the otherside of loop 70 into section 54, up through aperture 34 into section 56,under bight 42 into section 58 and away from the anchor member 12 insection 60. Similarly, limb 46 of the suture follows a path parallelwith that of limb 44 through the same sections as suture limb 44. Path29 results in formation of locking loop 70, the length L of which iseasily adjustable. The loop is created by the suture following the pathof sections 50, 52, 54, 56 and 58. Loop 70 is intended to receive agraft, generally folded on itself in the case of soft tissue (not shown)suspended from section 52.

In the preferred embodiment the two loop strands forming supporting loop70 are made of high strength, filamentous material such as ultra-highmolecular weight polyethylene and anchor member 12 is comprised ofimplantable grade titanium.

The invention facilitates the operation of device 10 by activating aloop length adjustment mechanism to resize the graft supporting loop byapplying tension to the construct in one direction (distally), andactivating an automatic loop locking mechanism by applying tension tothe construct in the opposite direction (proximally). In the preferredembodiment, the central bight 42 forms a locking loop 72 creatingdownward (as viewed in FIG. 3) pressure on the suture in section 58 dueto the downward force exerted on supporting loop 70 by the graft itself(not shown) adjacent section 52. This portion of section 52 is sometimesreferred to as a “saddle”. Locking loop 72 pushes the suture in section58 deeper into the pocket/recess 30 thus activating the lockingmechanism which causes the suture to engage the perimeter 32 andapertures 20, 22 thereby further increasing the friction created bylocking loop 72.

Adjustability of the loop length L is achieved by simply pulling on thefilament limbs 44 and 46 in section 60 in a distal direction away fromanchor member 12. This type of action simultaneously decreases thesize/length of the supporting loop and releases the pressure beingapplied by locking loop 72. When the desired size/length of thesupporting loop is achieved, tension is placed on the graft supportingloop 70 in the opposite, proximal direction so the locking loop 72automatically squeezes the suture limbs securely against anchor member12 to lock the suture limbs in place. The locking of the graftsupporting loop 70 is achieved due to the friction imparted on thefilament ends by the locking loop 72. As best seen in FIGS. 1 and 4,aperture 34 is angled relative to surfaces 24 and 26, and inclinedtoward apertures 20 and 22. This arrangement has been found to enhancethe friction between the suture and the surfaces and edges of the anchormember 12.

While the path of the preferred embodiment of device 10 is as shownabove, alternate embodiments are feasible. Thus, while the suture paththrough anchor member 12 results in device 10 comprising a graftsupporting element in the form of the aforementioned graft supportingloop member 70 suspended from anchor member 12, alternate embodiments ofdevice 10 are feasible in which bridge 28 between suture receivingapertures 20 and 22, is formed by a transverse pin in the middle of asingle opening (not shown). Such a structure would form a bridge and apair of apertures on either side of the pin.

Another alternate embodiment could comprise a different loopconstruction than that described above. As shown in FIGS. 2 through 4,loop member 70 is formed from a single length of suture or otherfilamentous material 40. In an alternate embodiment the loop could beformed by a plurality of individual suture loops (not shown) whichtogether form graft supporting loop 70. In yet another alternateembodiment loop 70 may be made to pass through an optional slidableflexible cylindrical sleeve 40 (not shown) situated at the section 52side of the supporting loop, opposite anchor member 12.

In yet another alternate embodiment, in order to facilitate orientingelongated anchor member 12 parallel to the bone tunnel axis and pullingit through the bone tunnel, an optional pulling-suture aperture 36 maybe formed at the leading end of the member 12.

In operation, device 10 serves to enable adjustment of loop length Lwhile also producing a relatively large graft fixation force. Anadvantage of this invention is its ability to provide graft fixation inbone tunnels shorter than those required for prior art suspensory graftrepairs. This invention is particularly useful for suspensory typerepairs of the ACL or PCL in situations where the bone tunnel length isrelatively short. For example, to perform an ACL surgery using aconventional transverse button on the lateral femoral surface, thesurgeon must drill a trans-femoral tunnel comprising a proximal graftreceiving portion and a smaller diameter distal portion having anopening at the bone tunnel exit onto the lateral femoral cortex. Thesurgeon must then precisely measure the overall tunnel length anddetermine the graft tunnel-contact length desired as well as the looplength required to achieve the desired contact between the tunnel walland the graft. The surgeon then calculates the drilling length of thegraft tunnel socket by selecting the length of graft desired to remainin the tunnel and, in the case of a button with a continuous (i.e.,endless) non-adjustable graft retaining loop, adding the distance neededto deploy (i.e., flip) the button. The reason the added distance isnecessary is because the button must completely exit the aperture priorto toggling perpendicular to the exit hole. This in turn requires thegraft to be pulled deeper into the bone tunnel, possibly evenmomentarily contacting the floor (end) of the socket. When this happensthe button can flip into a transverse orientation and when it is thenseated against the lateral femur the graft will pull back from thesocket floor, thereby leaving a gap between the socket floor and thegraft. A typical example of this would be a situation where there is anoverall trans-femoral tunnel length of 45 mm and where 20 mm of graft isdesired to remain in the tunnel and 15 mm is needed to deploy thebutton. In this case the surgeon would drill the proximal (main) portionof the femoral socket 35 mm deep. Once the procedure is completed therewill be excess space present between the femoral socket floor and thedistal end of the graft. At this point, if one were using conventionalnon-adjustable techniques and devices, the graft would be in its finalposition, that is, with a space between the graft and the socket floor.

On the other hand, as will be understood below, use of the subjectinvention enables the advantageous elimination of this excess space andthe maximization of graft contact with the bone tunnel wall where shorttrans-femoral tunnels are desired or encountered. That is, the method ofACL repair using the subject invention does not require a permanent,empty extra tunnel length to enable the button to turn.

The invention allows the graft retaining loop 70 to be sufficiently longso that the button may be passed through the femoral tunnel and deployedon the surface of the bone no matter how long the loop length is. Forexample, the loop length can be made long enough to enable the saddleportion of the supporting loop to be accessible from inside the jointand outside the femoral tunnel so that the saddle portion of the graftsupporting loop 70 may be engaged by the graft ligament (folded aboutloop 70) even after the button has been flipped. The graft ligament,thus supported directly by the plurality of individual loops making uploop 70, is then pulled into the bone tunnel by pulling the suture ends44 and 46 distally to shorten loop length L. The graft may be thuspulled into the tunnel until it contacts the socket floor. In eithercase, using this method it would be possible to even load the graft ontothe supporting loop outside the joint. Once the graft is in the correctposition an optional knot may be tied using limbs 44 and 46 to providesome additional resistance to any tendency of the limbs to pull out fromunder locking loop 72.

In the preferred embodiment the length of anchor member 12 may rangefrom 12 mm to 20 mm, the diameters of apertures 20 and 22 may be on theorder of 1 mm, the pocket/recess 30 may be in the range of 1 mm-2 mmwide and the suture diameter may be on the order of 1 mm or USP size #5.

An alternate embodiment of the invention is shown in FIG. 5 as device100. Device 100 comprises component parts identical to those of device10 with the sole exception being that the structure of filamentousstrand 140 is modified. That is, strand 140 is folded on itself toproduce a bight 142 from which extend two limbs 144 and 146, however,one of these limbs is passed (e.g., via piercing) through the lumen ofthe other end. Alternatively, as shown in FIG. 5, as the two limbs arethreaded through the suture receiving apertures (not seen in FIG. 5), ata point a short distance “S” below the anchor member, limb 144 passesthrough limb 146 and/or limb 146 passes through limb 144. This has theeffect of loosely securing the strand 140 to device 100 to thereby limittravel of the bight 142 when ends 144 and 146 are momentarily pulleddistally to resize the graft retaining loop.

The use of a single length of filamentous material folded on itself anddirected in a winding path facilitates the construction and operation ofdevice 10. In part this is because the bight 42 creates a locking loop72 due to the passage of the suture limbs 44, 46 under bight 42. It willbe understood, however, that an alternate embodiment could be formedfrom a single strand 240 of a hollow core suture instead of doublestrands 44, 46, as shown in FIG. 6. In this case, a separate shortstrand 242 of suture is folded on itself to create a bight element 244having only a loop 246, creating a locking loop 248, and a pair of veryshort limbs 250 and 252. The ends of the limbs 250, 252 of the shortstrand 242 are received a predetermined distance within the lumen 260 ofthe single hollow core suture 240. It will be understood that thisconstruct operates like a “finger trap” wherein tension on the end ofsuture 240 will cause it to constrict around legs 250, 252.

It will be understood by those skilled in the art that numerousimprovements and modifications may be made to the preferred embodimentof the invention disclosed herein without departing from the spirit andscope thereof

What is claimed is:
 1. A suspensory graft fixation device for securing areplacement graft ligament in a bone tunnel comprising: an elongatedanchor member adapted to be situated transversely adjacent the distalend of said bone tunnel and comprising a plurality of apertures; a graftsupporting loop element attached to said anchor member, said graftsupporting loop element formed of a suture threaded through saidapertures in a predetermined path and adapted to support saidreplacement graft ligament in said bone tunnel proximally of said distalend and at a selected predetermined distance from said distal end; andmeans for automatically locking said graft supporting loop element atsaid predetermined distance.
 2. A suspensory graft fixation deviceaccording to claim 1 further comprising means for adjusting saidpredetermined distance.
 3. A suspensory graft fixation device accordingto claim 2 wherein said predetermined path comprises a first portionwherein said suture is situated distally of suture in a second portionand wherein said suture in a second portion may be selectivelycompressed by suture in said first portion against said anchor member.4. A suspensory graft fixation device according to claim 3 wherein saidfirst portion is in the form of a bight.
 5. A suspensory graft fixationdevice according to claim 3 comprising means for moving said suture in asecond portion distally to release pressure applied on said suture in asecond portion by suture in said first portion.
 6. A suspensory graftfixation device according to claim 3 wherein said suture comprises atleast one suture end distally extending from said anchor member andwherein said means for adjusting is activated by moving said suture enddistally relative to said anchor until said replacement graft ligamentis situated at said selected predetermined distance.
 7. A suspensorygraft fixation device according to claim 3 wherein said means forautomatically locking is activated by tension applied to said graftsupporting loop element in a proximal direction causing the bight tofrictionally engage the graft supporting loop between the bight and theelongated anchor.
 8. A suspensory graft fixation device according toclaim 3 wherein said anchor member comprises a top surface and a bottomsurface, wherein said plurality of apertures pass through said anchormember from said top surface to said bottom surface, wherein saidplurality of apertures comprises a pair of suture receiving aperturesfor receiving suture passing therethrough in a proximal direction and asuture return aperture for receiving suture passing therethrough in adistal direction.
 9. A suspensory graft fixation device according toclaim 8 further comprising a bridge portion for suspending said graftsupporting loop element and means for joining said limbs at a pointproximal to said anchor member in order to minimize the movement of saidsuture in a first portion away from said anchor member.
 10. A suspensorygraft fixation device according to claim 9 wherein said joinder iseffected by passing at least one limb through the other to create amovable junction between said limbs.
 11. A suspensory graft fixationdevice according to claim 8 wherein said suture receiving apertures arerecessed a predetermined distance below said top surface to form atortuous path to frictionally engage said graft supporting loop element.12. A suspensory graft fixation device for securing a replacement graftligament in a bone tunnel comprising: an elongated anchor member adaptedto be situated transversely adjacent the exit of said bone tunnel, saidanchor member comprising a top surface and a bottom surface; a graftsupporting loop element connected to said anchor member and saidreplacement graft ligament; a suture folded on itself to form a pair ofparallel suture limbs extending from a bight and threaded along apredetermined path relative to selected portions of said elongatedanchor member such that said suture forms said bight and selectedportions of said graft supporting looping element; parallel aperturesextending from said top surface to said bottom surface, said aperturesreceiving said parallel suture limbs, which limbs are urged by saidbight locking loop against said top surface; a suture return aperture insaid anchor member for receiving said parallel suture limbs and meansfor passing said limbs between said bight and said top surface.
 13. Asuspensory graft fixation device according to claim 12 furthercomprising a bridge portion for suspending said graft supporting loopelement and means for joining said limbs at a point proximal to saidanchor member in order to minimize the movement of said bight away fromsaid anchor member.
 14. A suspensory graft fixation device for securinga replacement graft ligament in a bone tunnel comprising: an elongatedanchor member adapted to be situated transversely adjacent the distalend of said bone tunnel and comprising a plurality of apertures; a graftsupporting loop element attached to said anchor member, said graftsupporting loop element formed of a suture threaded through saidapertures in a predetermined path and adapted to support saidreplacement graft ligament in said bone tunnel proximally of said distalend of said bone tunnel and at a selected predetermined distance fromsaid distal end of said bone tunnel; and means for automatically lockingsaid graft supporting loop element to maintain said replacement graftligament at said predetermined distance, said means for automaticallylocking comprising a first portion of said suture which is used to formsaid graft supporting loop element and a second portion of said suturewhich is used to exert a locking force on said first predeterminedportion of said suture.
 15. A suspensory graft fixation device forsecuring a replacement graft ligament in a bone tunnel comprising: anelongated anchor member adapted to be situated transversely adjacent theexit of said bone tunnel, said anchor member comprising a plurality ofapertures extending between a top surface and a bottom surface of saidanchor member; a suture with a hollow core, said suture having aproximal end and a distal end, said suture threaded along apredetermined path wherein said proximal end of said hollow core sutureis situated at a point proximal to said anchor member, and said distalend is situated at a point distal to said anchor member, a portion ofsaid predetermined path formed into a graft supporting loop element forconnecting said anchor member and said replacement graft ligament; abight element formed by a suture folded on itself to form a bight and apair of parallel suture limbs extending from said bight; a pair ofparallel apertures extending through said anchor member from said topsurface to said bottom surface, wherein said parallel apertures receivesaid parallel suture limbs and said bight is situated adjacent said topsurface of said anchor member, and wherein said parallel suture limbsare received within said proximal end of said hollow core suture; asuture return aperture for receiving said distal end of the hollow coresuture opposite the proximal end which receives said parallel suturelimbs; and means for passing said distal end of said hollow core suturebetween said bight and said top surface.
 16. A suspensory graft fixationdevice according to claim 7, wherein said predetermined distance isadjustable by tension applied to said graft supporting loop element inan opposite, distal direction.